Gate-Voltage-Induced Magnetization Reversal and Tunneling Anisotropic Magnetoresistance in a Single Molecular Magnet with Temperature Gradient

We study the coutrol of gate voltage over the magnetization of a single-molecule magnet （SMM） weakly coupled to a ferromagnetic and a normal metal electrode in the presence of the temperature gradient between two electrodes. It is demonstrated that the SMM＇s magnetization can change periodically with periodic gate voltage due to the driving oI the temperature gradient. Under an appropriate matching of the electrode polarization, the temperature difference and the pulse width of gate voltage, the SMM＇s magnetization can be completely reversed in a period of gate voltage. The corresponding flipping time can be controlled by the system parameters. In addition, we also investigate the tunneling anisotropic magnetoresistance （TAMFt） of the device in the steady state when the ferromagnetic electrode is noncollinear with the easy axis of the SMM, and show the jump characteristic of the TAMR.

Phonon-Assisted Spin Current in Single Molecular Magnet Junctions

Owing to the bistable character of the single molecular magnet （SMM）, it can generate 100% spin-polarized currents even connected with normal （N） leads. In this work, we study the phonon-assisted spin current in N- SMM-N systems. We mainly focus on the interplay of SMM＇s bistable character and electron-phonon coupling. It is found that when SMM is trapped in one of the lowest bistable states, it can generate phonon-assisted spin- polarized currents. At the up-spin transport channel, it is accompanied by a phonon-assisted up-spin current, while at the down-spin transport channel, it is accompanied by a phonon-assisted down-spin current.

Global entanglement in ground state of {Cu_3} single-molecular magnet with magnetic field

We investigate global entanglement in the ground state of single-molecular magnet Na9[Cu3Na3（H2O）9（α- AsW9O33）2]-26H2O with an external magnetic field. The concurrence, tangle, and measure function Q, which characterize the pairwise entanglement, 3-party entanglement and total entanglement, respectively, are calculated numerically at zero temperature. The results show that the magnitude and direction of the applied magnetic field play a significant role in the properties of three kinds of entanglement measures. We give a physical interpretation of the variation of the global entanglement with the magnetic field. Finally, the phase diagram of the global entanglement characterized by the critical magnetic fields is presented.

Controllable Optical Bistability in a Crystal of Molecular Magnets System

We investigate the formation of optical bistabifity (OB) in a crystal of molecular magnets contained in aunidirectional ring cavity.The crystal is subjected to one dc magnetic field and two (probe and coupling) ac resonantmagnetic field.The results show that OB can be controlled efficiently by adjusting the intensity of the control field,the detuning of probe magnetic field and the cooperation parameter.FUrthermore,within certain parameter range,theoptical multistablity (OM) can also be observed in the crystal medium.This investigation can be used for designing newtypes of nonelectronic devices for realizing switching process.

Macroscopic Quantum Coherence in Antiferromagnetic Molecular Magnets

The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis of instanton technique in the spin-coherent-state path-integral representation, both the rigorous Wentzel-Kramers-Brillouin exponent and pre-exponential factor for the ground-state tunnel splitting are obtained. We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys. Rev. Lett. 80 (1998) 169), but also have great influence on the intensity of the ground-state tunnel splitting. Those features clearly have no analogue in the ferromagnetic molecular magnets. We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets. The analytical results are complemented by exact diagonalization calculation.

Effects of Arbitrarily Directed Field on Spin Phase Oscillations in Biaxial Molecular Magnets

Quantum phase interference and spin-parity effects are studied in biaxial molecular magnets in a magnetic field at an arbitrarily directed angle. The calculations of the ground-state tunnel splitting are performed on the basis of the instanton technique in the spin-coherent-state path-integral representation, and complemented by exactly numerical diagonalization. Both the Wentzel-Kramers-Brillouin exponent and the pre-exponential factor are obtained for the entire region of the direction of the field. Our results show that the tunnel splitting oscillates with the field for the small field angle, while for the large field angle the oscillation is completely suppressed. This distinct angular dependence, together with the dependence of the tunnel splitting on the field strength, provides an independent test for spin-parity effects in biaxial molecular magnets. The analytical results for the molecular Fes magnet are found to be in good agreement with the numerical simulations, which suggests that even the molecular magnet with total spin S = 10 is large enough to be treated as a giant spin system.

Development and in vitro study of a bi-specific magnetic resonance imaging molecular probe for hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma(HCC)ranks second in terms of cancer mortality worldwide.Molecular magnetic resonance imaging(MRI)targeting HCC biomarkers such as alpha-fetoprotein(AFP)or glypican-3(GPC3)offers new strategies to enhance specificity and help early diagnosis of HCC.However,the existing iron oxide nanoparticle-based MR molecular probes singly target AFP or GPC3,which may hinder their efficiency to detect heterogeneous micro malignant HCC tumors<1 cm(MHCC).We hypothesized that the strategy of double antibody-conjugated iron oxide nanoparticles which simultaneously target AFP and GPC3 antigens may potentially be used to overcome the tumor heterogeneity and enhance the detection rate for MRI-based MHCC diagnosis.AIM To synthesize an AFP/GPC3 double antibody-labeled iron oxide MRI molecular probe and to assess its impact on MRI specificity and sensitivity at the cellular level.METHODS A double antigen-targeted MRI probe for MHCC anti-AFP-USPIO-anti-GPC3(UAG)was developed by simultaneously conjugating AFP andGPC3 antibodies to a 5 nm ultra-small superparamagnetic iron oxide nanoparticle(USPIO).At the same time,the singly labeled probes of anti-AFP-USPIO(UA)and anti-GPC3-USPIO(UG)and non-targeted USPIO(U)were also prepared for comparison.The physical characterization including morphology(transmission electron microscopy),hydrodynamic size,and zeta potential(dynamic light scattering)was conducted for each of the probes.The antigen targeting and MRI ability for these four kinds of USPIO probes were studied in the GPC3-expressing murine hepatoma cell line Hepa1-6/GPC3.First,AFP and GPC3 antigen expression in Hepa1-6/GPC3 cells was confirmed by flow cytometry and immunocytochemistry.Then,the cellular uptake of USPIO probes was investigated by Prussian blue staining assay and in vitro MRI(T2-weighted and T2-map)with a 3.0 Tesla clinical MR scanner.RESULTS Our data showed that the double antibody-conjugated probe UAG had the best specificity in targeting Hepa1-6/GPC3 cells expressing AFP and GPC3 antigens compared with single antibody-conjugated and unconjugated USPIO probes.The iron Prussian blue staining and quantitative T2-map MRI analysis showed that,compared with UA,UG,and U,the uptake of double antigen-targeted UAG probe demonstrated a 23.3%(vs UA),15.4%(vs UG),and 57.3%(vs U)increased Prussian stained cell percentage and a 14.93%(vs UA),9.38%(vs UG),and 15.3%(vs U)reduction of T2 relaxation time,respectively.Such bi-specific probe might have the potential to overcome tumor heterogeneity.Meanwhile,the coupling of two antibodies did not influence the magnetic performance of USPIO,and the relatively small hydrodynamic size(59.60±1.87 nm)of double antibodyconjugated USPIO probe makes it a viable candidate for use in MHCC MRI in vivo,as they are slowly phagocytosed by macrophages.CONCLUSION The bi-specific probe presents enhanced targeting efficiency and MRI sensitivity to HCC cells than singly-or non-targeted USPIO,paving the way for in vivo translation to further evaluate its clinical potential.

Dynamic Stiffness Analysis and Experimental Verification of Axial Magnetic Bearing Based on Air Gap Flux Variation in Magnetically Suspended Molecular Pump

Current and displacement stiffness are important parameters of axial magnetic bearing(AMB)and are usually considered as constants for the control system.However,in actual dynamic work situations,time-varying force leads to time-varying currents and air gap with a specific frequency,which makes the stiffness of appear decrease and even worsens control performance for the whole system.In this paper,an AMB dynamic stiffness model considering the flux variation across the air gap due to frequency is established to obtain the accurate dynamic stiffness.The dynamic stiffness characteristics are analyzed by means of the dynamic equivalent magnetic circuit method.The analytical results show that the amplitude of current and displacement stiffness decreases with frequency increasing.Moreover,compared with the stiffness model without considering the variation of flux density across the air gap,the improved dynamic stiffness results are closer to the actual results.Through the dynamic stiffness measurement method of AMB,experiments of AMB in magnetically suspended molecular pump(MSMP)are carried out and the experimental results are consistent with theoretical analysis results.This paper proposes the dynamic stiffness model of axial magnetic bearing considering the variation of flux density across the air gap,which improves the accuracy of the AMB stiffness analysis.

Diffusion magnetic resonance imaging: A molecular imaging tool caught between hope, hype and the real world of “personalized oncology”

"Personalized oncology" is a multi-disciplinary science, which requires inputs from various streams for optimal patient management. Humongous progress in the treatment modalities available and the increasing need to provide functional information in addition to the morphological data; has led to leaping progress in the field of imaging. Magnetic resonance imaging has undergone tremendous progress with various newer MR techniques providing vital functional information and is becoming the cornerstone of "radiomics/radiogenomics". Diffusionweighted imaging is one such technique which capitalizes on the tendency of water protons to diffuse randomly in a given system. This technique has revolutionized oncological imaging, by giving vital qualitative and quantitative information regarding tumor biology which helps in detection, characterization and post treatment surveillance of the lesions and challenging the notion that "one size fits all". It has been applied at various sites with different clinical experience. We hereby present a brief review of this novel functional imaging tool, with its application in "personalized oncology".

Influence of a strong magnetic field on the hydrogen molecular ion using B-spline-type basis-sets

As an improvement on our previous work [J. Phys. B： At. Mol. Opt. Phys. 45 085101（2012）], an accurate method combining the spheroidal coordinates and B-spline basis is applied to study the ground state 1σg and low excited states1σu, 1πg,u, 1δg,u, 2σg of the H＋2in magnetic fields ranging from 10^9Gs（1 Gs = 10^-4T） to 4.414 × 10^13 Gs. Comparing the one-center method used in our previous work, the present method has a higher precision with a shorter computing time.Equilibrium distances of the states of the H＋2in strong magnetic fields were found to be accurate to 3-5 significant digits（s.d.） and the total energies 6-11 s.d., even for some antibonding state, such as 1πg, which is difficult for the one-center method to give reliable results while the field strength is B ≥ 10^13 Gs. For the large disagreement in previous works, such as the equilibrium distances of the 1πg state at B = 10^9 Gs, the present data may be used as a reference. Further, the potential energy curves（PECs） and the electronic probability density distributions（EPDDs） of the bound states 1σg, 1πu, 1δg and antibonding states 1σu, 1πg, 1δu for B = 1, 10, 100, 1000 a.u.（atomic unit） are compared, so that the different influences of the magnetic fields on the chemical bonds of the bound states and antibonding states are discussed in detail.

Star Formation in Magnetized, Turbulent and Rotating Molecular Cloud: The Critical Mass

In this paper, we present the critical mass of magnetized, turbulent and rotating star-forming molecular cloud core (MCc) in the presence of magnetic tension. The critical mass of star-forming magnetized cloud is influenced by the magnetic tension, magnetic pressure and other pressures. Applying the method of theoretical modelling by taking into account the basic equations and assumptions, we formulate the critical mass of magnetized MCc in different cases. Accordingly, the minimum critical masses we find in both cases are different. Energy due to magnetic tension significantly triggers the collapse at relatively larger radius of the core. The model shows that when the initial radius of the parent cloud (Ro) is larger than that of collapsing core radius (Rcore) the magnetic tension also has the larger radius of curvature, so it plays a significant role in supporting gravity to collapse the core. The results indicate gravity without magnetic tension may not overcome magnetic pressure, turbulence pressure and pressure due to rotation. This shows the critical mass of MCc for the collapse depends on the tension force that magnetic field lines apply on the envelope. We conclude that if there is magnetic pressure in star-forming MCc, there is also unavoidable magnetic tension, which triggers the collapse of the core. If there is no magnetic tension, the magnetized MCc needs relatively larger mass and higher density within the small size to collapse.

Study of structural and magnetic properties of Fe(80)P-9B(11) amorphous alloy by ab initio molecular dynamic simulation

The structural and magnetic properties of Fe80P9B11 amorphous alloy are investigated through ab initio molecular dynamic simulation. The structure evolution of Fe（80）P9B（11） amorphous alloy can be described in the framework of topological fluctuation theory, and the fluctuation of atomic hydrostatic stress gradually decreases upon cooling. The left sub peak of the second peak of Fe–B partial pair distribution functions（PDFs） becomes pronounced below the glass transition temperature, which may be the major reason why B promotes the glass formation ability significantly. The magnetization mainly originates from Fe 3d states, while small contribution results from metalloid elements P and B. This work may be helpful for developing Fe-based metallic glasses with both high saturation flux density and glass formation ability.

DES磁性分子印迹材料的制备及其吸附分离性能

利用溶剂热法制备纳米Fe 3 O 4,并将其分散在正硅酸乙酯(TEOS)水解液中,在表面沉积一层SiO_(2).用甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)对SiO_(2)-Fe 3 O 4表面改性,得到MPS-SiO_(2)-Fe 3 O 4.将甲基丙烯酸(MAA)与己烯雌酚(DES)以摩尔比4∶1加入乙腈溶剂中,进行12 h自组装,再加入MPS-SiO_(2)-Fe 3 O 4、乙二醇二甲基丙烯酸酯(EGDMA)和偶氮二异丁腈(AIBN),进行超声分散30 min,65℃条件下机械搅拌,反应24 h,制得DES磁性分子印迹聚合物(MMIP).采用透射电镜、振动样品磁强计和吸附试验等方法进行表征分析.结果表明:MMIP的饱和磁化强度为268 kA/m,无磁滞现象,矫顽力为0,表现出超顺磁性,在磁铁作用下17 s就可与溶液分离;室温下,MMIP对DES的静态最大吸附量为7.1 mg/g,动态吸附时MMIP在60 min时可以达到静态最大吸附量的90%以上;MMIP对DES的印迹因子为3.70,因而对DES有较大的识别能力;MMIP可重复使用6次以上,具有良好的再生循环性能.

Characterization of Average Molecular Structure of Heavy Oil Fractions by ~1H Nuclear Magnetic Resonance and X-ray Diffraction

The chemical structure of heavy oil fractions obtained by liquid-solid adsorption chromatography was character-ized by 1 H nuclear magnetic resonance and X-ray diffraction.The molecular weight and molecular formula of asphaltene molecules were estimated by combining 1 H nuclear magnetic resonance and X-ray diffraction analyses,and were also ob-tained from vapor pressure osmometry and elemental analysis.Heteroatoms,such as S,N,and O atoms,were considered in the construction of average molecular structure of heavy oils.Two important structural parameters were proposed,including the number of alkyl chain substituents to aromatic rings and the number of total rings with heteroatoms.Ultimately,the av-erage molecular structures of polycyclic aromatics,heavy resins and asphaltene molecules were constructed.The number of α-,β-,γ-,and aromatic hydrogen atoms of the constructed average molecular structures fits well with the number of hydro-gen atoms derived from the experimental spectral data.

磁共振髓鞘探针Gd-DTDAS在多发性硬化大鼠髓鞘损伤模型中的实验研究

目的探讨MRI对比剂Gd-DTDAS在多发性硬化(multiple sclerosis,MS)大鼠髓鞘损伤模型中的应用价值。材料与方法细胞实验中,将少突胶质细胞前体细胞(oligodendrocyte precursor cells,OLN-93)随机分为对照组2(n=3)和溶血磷脂酰胆碱(lysophosphatidylcholine,LPC)组(n=3),LPC组细胞置于无菌共聚焦培养皿中与1 mL 800μM LPC溶液共孵育30 min。通过噻唑蓝比色法(methyl thiazolyl tetrazolium,MTT)评价细胞毒性,计算OLN-93与Gd-DTDAS共孵育24 h后的吸光度和存活率;细胞摄取实验中,对照组2和LPC组对比,定量两组细胞对Gd-DTDAS的摄取值以及相应荧光强度的变化。动物实验中,将6~8周龄SD大鼠随机分为对照组(n=12)与实验组(n=18),实验组大鼠左侧胼胝体注射1%LPC溶液(1%LPC溶于PBS)。造模后(1、3、7 d)进行行为学观察,并在注射后7天进行T1WI及T2WI序列扫描。根据MRI异常信号部位进行大鼠脑组织Gd-DTDAS染色(n=6)以及浸泡(n=6),评估Gd-DTDAS与髓鞘部位的结合情况,其中,染色实验分组命名为对照组3与实验组3,浸泡实验分组命名为对照组4与实验组4;通过尾静脉注射Gd-DTDAS,MR评估实验组(n=6)注射Gd-DTDAS前后大脑髓鞘变化。结果细胞毒性实验中,当Gd-DTDAS浓度增加到400μM时,OLN-93细胞的存活率约为95%,细胞存活率差异无统计学意义(t=4.20,P>0.05)。细胞摄取实验中,两组细胞均能摄取Gd-DTDAS,LPC组摄取量显著低于对照组2,差异具有统计学意义(t=31.75,P<0.01)。动物体外实验中,与对照组3比较,Gd-DTDAS染色的实验组3脑组织切片荧光强度显著下降,差异有统计学意义(U=9,P<0.01);Gd-DTDAS浸泡中,对照组4(n=6)与实验组4(n=6)脑组织切片浸泡后MRI分辨率显著升高,差异有统计学意义(对照组4,t=8.76,P<0.01)(实验组4,t=2.89,P<0.01)。体内实验中,与尾静脉注射前比较,注射后胼胝体区域MRI T1maps弛豫性显著降低(t=14.46,P<0.01)。结论髓鞘探针Gd-DTDAS能够更好地结合髓磷脂丰富的区域,髓鞘靶向MRI显像更佳,能特异性显示多发性硬化髓鞘损伤部位。

磁悬浮分子泵转子振动抑制研究

磁悬浮分子泵具有工作转速高、转子极转动惯量大等特点,针对磁悬浮分子泵转子在升速过程中出现的弯曲模态振动以及涡动模态振动,提出了一种基于滤波交叉反馈与陷波器的大转动惯量磁悬浮转子控制方法。建立磁悬浮轴承-大转动惯量刚性转子系统数学模型,求解得出转子涡动模态频率,根据该模型分析了滤波交叉反馈控制器对涡动模态振动的抑制效果,并且设计了陷波器用于抑制不同转速下的转子弯曲模态振动。试验结果表明,磁悬浮分子泵稳定升速至工作转速18000 r/min,转子振动位移为35μm,弯曲模态振动以及涡动模态振动得到了有效抑制。

页岩油流体赋存状态研究方法现状综述

概述了页岩油流体赋存状态基本概念和特点,总结并对比了页岩油流体赋存状态的研究方法,包括核磁共振法、溶剂分步抽提法、分步热解法、扫描电镜、数值模拟方法和分子模拟方法等。对目前页岩油流体赋存状态研究现状进行总结,并对未来研究进行展望。

基于MRI影像组学在乳腺癌分子分型的研究进展

乳腺癌严重影响女性身心健康,是女性最常见的恶性肿瘤,其依据病理不同进行分子分型,早期识别病理分型和靶向治疗是改善患者预后的关键。病理虽为金标准也存在一定不足,如操作的有创性、标本取材的局限性以及检测时间要求的限制性。影像组学通过深度挖掘影像图像多维度特征,将肿瘤的异质性进行量化处理,采用一种无创性、简便的方法对肿瘤的生物学特性进行综合评价,在乳腺癌分子分型的发现、预测淋巴结转移、制订治疗方案、评估治疗效果、判断患者预后等方面已得到广泛应用。现拟基于MRI影像组学特征对乳腺癌分子分型的应用现状进行综述。

MRI影像组学预测非特殊型浸润性乳腺癌分子分型的价值

目的 探讨基于MRI影像组学预测非特殊型浸润性乳腺癌Luminal型和非Luminal型的临床价值。材料与方法 回顾性分析本院2021年4月至2022年12月经病理证实为非特殊型浸润性乳腺癌的患者149例,均在治疗前两周进行了MRI平扫和增强扫描。收集全部入组患者的临床及病理资料,根据雌激素受体(estrogen receptor,ER)和孕激素受体(progesterone receptor,PR)的表达情况将患者分为Luminal型(n=90)和非Luminal型(n=59)。以7∶3的比例随机将其分为训练组(n=104)和测试组(n=45)。将提取的数据进行降维并筛选影像组学最优特征,基于随机森林法建立三个预测模型,分别是扩散加权成像(diffusion weighted imaging,DWI)序列模型、动态对比增强(dynamic contrast-enhanced,DCE)-MRI序列模型以及DWI和DCE序列联合模型。采用受试者工作特征(receiver operating characteristic,ROC)曲线下面积(area under the curve,AUC)评价模型的预测性能。不同模型的预测效能采用DeLong检验进行比较。结果 Luminal型和非Luminal型组间、训练组和测试组组间患者的临床病理特征(年龄、ER状态、PR状态、绝经状态、淋巴结转移情况)差异均无统计学意义(P>0.05)。DWI模型、DCE模型和联合模型在训练组中的AUC分别为0.859、0.839、0.903,在测试组中的AUC分别为0.722、0.798、0.821。DeLong检验显示训练组的DCE模型和联合模型预测效能差异有统计学意义(P=0.03),除此之外三个模型两两比较预测效能差异均无统计学意义(P>0.05)。结论 基于MRI影像组学构建的模型可以较好地预测非特殊型浸润性乳腺癌Luminal型和非Luminal型,并能为非特殊型浸润性乳腺癌临床治疗方案的决策提供帮助。

浸润性乳腺癌动态增强磁共振与分子分型的相关性分析

目的探讨浸润性乳腺癌动态增强磁共振影像特征及其与分子分型的相关性,以指导临床选择合适的治疗方案。方法选取经手术病理证实的57例浸润性乳腺癌患者资料,分析患者的DCE-MRI影像学特征。根据瘤体免疫组织化学的雌激素受体(ER)、孕激素受体(PR)、人类表皮生长因子受体-2(HER-2)及Ki-67的表达情况,将乳腺癌分为Luminal A型、Luminal B型、HER-2过表达型及三阴性四个亚型,比较不同分子亚型乳腺癌的DCE-MRI影像学特征。结果57例患者中Luminal A型占21.1%(12/57),Luminal B型占47.4%(27/57),HER-2过表达型占17.5%(10/57),三阴性乳腺癌占14.0%(8/57);Luminal型乳腺癌MRI检查表现为不规则或分叶状肿块,三阴性乳腺癌边缘较光整且呈环形强化,HER-2过表达型通常为快进快出的强化模式,即Ⅲ型TIC曲线类型。结论不同分子分型的乳腺癌动态增强磁共振的形态学和血流动力学具有相应的特征,可辅助指导临床选择治疗方案并判断预后。